The limited support for HIV prevention/control in Africa will not enable expensive programs of the type now present in developed countries. Individual-orientated approaches may not be sufficient. Effective strategies must be informed by a clear understanding of the African context. Based on the apparent efficacy of peer outreach as an intervention strategy in the USA, several "demonstration" projects have recently sprung up in Africa, including in Kinshasa, Democratic Republic of Congo. Yet the efficacy of this attractive/inexpensive approach remains poorly evaluated in Africa. To promote research infrastructure in behavioral science, epidemiology and research methodology (behav/epi/research), Kinshasa School of Public Health (KSPH) proposes to partner with the Schools of Public Health at the University of North Carolina (UNC) and Johns Hopkins University (JHU) to improve its behav/epi/research capacity. The investigators will first establish a KSPH Research Unit as a focus for research and research training in the KSPH MPH curriculum. Current UNC/JHU shared Fogarty AITRP funds will then enable medium and long term training in behav/epi/research at UNC and JHU. As a pedagogic paradigm 2 randomized, controlled intervention studies to assess efficacy of peer education to decrease risk of sexually transmitted infections (STIs) including HIV will be performed. KSPH/UNC/JHU will partner with two effective front-line Kinshasa non-governmental community-based organizations, Carrefour des Jeunes (Crossroads for Youth) and Centre STD Matonge to conduct peer leader/network studies in teenagers (TAs) and young female sex workers (CSWs) with a recent STI other than HIV. The experimental condition is a peer outreach education condition and the equal attention control condition is an individually-focused social cognitive condition. Both studies will include 400 index participants (TAs or CSWs with a recent STI other than HIV) randomly assigned to one of the two conditions (200/condition) and 2 randomly chosen peer network members of each index, for a total of 1200 TAs and 1200 CSWs. Outcome evaluation in each trial will include pre-test/post-test assessments of 400 index participants and 800 of their peer network members at 3, 6, 12 and 18 months post intervention. Main outcome measures will be self reported sexual risk behaviors and STI/HIV incidence. The work will inform HIV prevention policy and strengthen research and training at KSPH